|Serena Williams Pregnant|
Williams, 35, did not comment beyond the photo and two-word caption.
Williams got engaged to Reddit co-founder Alexis Ohanian in December.
Williams hasn't played since winning the Australian Open in late January. She pulled out of her next two scheduled events -- Indian Wells and Miami -- citing a left knee injury. Her only other tournament this year was in Auckland, New Zealand, where she lost in the round of 16.
Tennis' next major event is the French Open, which begins on May 28. If Williams is, in fact, 20 weeks pregnant, she would be due in early September.